Setting mechanism for secondary clocks

ABSTRACT

A master-secondary clock system in which a master clock having a high order of accuracy, acts to regulate the operation of a plurality of remotely disposed secondary clocks. This is accomplished by means of a direct-current control pulse which is transmitted to the secondary clocks from the master clock, and is received at each secondary clock by an electromagnetic setting mechanism adapted to reset the seconds hand of the secondary clock to bring it into registration with the seconds hand of the master clock. The setting mechanism is also adapted to shift the hour hand of the secondary clock one hour ahead or back, depending on whether a transfer is to be made from Standard to Daylight Savings time or vice versa, this action being effected concurrently with the resetting of the seconds hand, but only when the control pulse is transmitted during a predetermined interval in the course of the day, the direction of shift depending on the polarity of the control pulse.

[111 3,739,568 June 19, 1973 ABSTRACT SETTING MECHANISM FOR SECONDARY CLOCKS A master-secondary clock system in which a master [75 1 Inventor Egbert Van Hdaflen Closter clock having a high order of accuracy, acts to regulate '[73] Assignee: Bulova Watch Company, Inc., New

the operation of a plurality of remotely disposed secondary clocks. This is accomplished York, N.Y.

by means of a direct-current control pulse which is transmitted to the secondary clocks from the master clock, and is received at each secondary clock by an electroma [22] Filed: Feb. 14, 1972 gnetic setting mechanism adapted to reset the seconds hand [211 App]. No.: 225,834

of the secondary clock to bring it into registration with the seconds hand of the master clock. The setting mechanism is also adapted to shift the hour hand of th secondary clock one hour ahead or back e depending on whether a transfer is to be made from Standard to Daysmes MM /24 w54 smurfs, mww B 756 555 4W 6 05 mmmmm 4, 6 w .m n u 38 n 5 S a w W m T. m m 5 m N m u i "R E m mmm M ""5 U m ml m ""3 A mam 8 u, m t s s mem mm E Na u" T wy w mm mA m wmm. U m rTh uoh m a .RSCMDFB "h e n c RD N m .E 512 n T 94677 0 s wwwww C G 556n7 d S sud U fi uunmm I ,J 22865 n um m 54821 5 55 5 42,1506, fl 2333 S ef ddeho ntt GOO- a .mwmo es l m em f nrmtu Uf c S eem. N a .w m m w m .F a S m a m eran :l mrtve W ove p vhome m t -d i so ..hd n 6 ehv r nmm m mfim m mnwa e i e S ..C. .1 i dd 8 SUne p H COrrl. .mmt mm v ua t a b mn d t t d.m s mb mmw hkhddm Primary Examiner-Richard B. Wilkinson Assistant Examiner U. Weldon Attorney-Michael Ebert villi,

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H F i :2 5/11 a ng meg-1% SETTING MECHANISM FOR SECONDARY CLOCKS BACKGROUND OF THE INVENTION This invention relates generally to master-secondary clock systems, and more particularly toan electromagnetic setting mechanism for automatically correcting the settings of the hour and seconds hands of all secondary clocks in the system.

In a conventional master-secondary clock system, a master clock located at a central control station functions to regulate the operation of secondary clocks disposed at various remote points. Such systems are presently in use in railroads, office buildings, radio stations and in other facilities where it is important that the correct time be indicated at many points distributed throughout the facility so that activity carried out at these points may be properly coordinated.

In a typical installation, the master clock is designed to keep accurate time and to supply control or sync signals to the various secondary clocks. These signals actuate a setting mechanism for bringing the setting of the hour, minute and seconds hands of the secondary clocks into step with the hands of the master clock. Such systems are often quite elaborate, and may include a thousand or more secondary clocks.

When the secondary clocks in the system are of the A-C motor type, the most common problem encountered is that of power failure, for while the master clock is usually provided with an auxiliary power supply to keep it going in the event of power failure, the secondary clocks stop functioning upon loss of power. With the restoration of power, which may take place several hours later, correction of the secondary clocks cannot be efi'ected automatically, for while the typical system is adapted to correct for relatively minor time displacements between the master and the secondaries, when a gross displacement arises, correction cannot be carried out by the mechanism ordinarily provided for this purpose.

Hence, with master-clock systems of the type heretofore known, a prolonged power failure makes necessary a manual resetting of each secondary clock so that the setting mechanism may thereafter be capable of maintaining the secondaries in step with the master.

Quite apart from the problem of power failure is the matter of setting the secondary clocks one hour ahead or back when going from Standard to Daylight Savings time or vice versa. This one full hour adjustment is presently carried out manually on the appropriate days of the year. Where a thousand or more secondaries are involved, this manual operation makes it necessary to enlist a team of technicians who are required to travel to and correct all secondaries in the system.

SUMMARY OF THE INVENTION In view of the foregoing, the main object of this invention is to provide a master-secondary clock system wherein all secondaries include an electro-magnetic setting mechanism that is responsiveto a direct-current control pulse transmitted from the master and functions to set both the seconds hand and the hour hand.

More specifically, it is an object of this invention to provide a setting mechanism of the above type which, when actuated by a D-C control pulse, regardless of its polarity, will function to aetthe seconds hand to the 60" position but which, when the control pulse is transmitted during a specified interval in the course of the day, will at the same time act to bring about a 1- hour shift of the hour hand in a direction determined by the polarity of the pulse, thereby effecting a transfer from Standard to Daylight Savings time or vice versa.

Also an object of this invention is to provide a battery-operated master-secondary clock system which is independent of the A-C power line, the system nevertheless providing highly accurate time indications.

Among the significant advantages of a system in accordance with this invention is that it continues to function in the event of an A-C power failure, no mechanical resetting of the secondaries being necessary at any time, even when switching from Standard to Daylight Savings time.

Briefly stated, these objects are attained in a batteryoperated mastersecondary clock system wherein each secondary is provided with a setting mechanism including an electromagnetic device or motor which is responsive to a DC pulse transmitted by the master clock. The motor serves to turn a drive wheel in a direction determined by the pulse polarity. The wheel, when driven, operates both a seconds hand setting assembly and an hour hand setting assembly.

The seconds hand assembly includes a lever which, when the wheel is turned in either direction, is caused to engage a cam keyed to the seconds hand arbor, the cam acting to set the seconds hand to the position, the lever thereafter being retracted.

The hour hand assembly includes a cam mounted on the hour hand shaft, the cam having two spaced slots therein which is engageable by the arms of a lever during a predetermined interval in the course of a day. When the wheel is turned in one direction during this interval, one arm of the lever acts to engage the first slot in the cam to cause the hour hand to move ahead one hour, and when the wheel is turned in the reverse direction, the other arm of the lever acts to engage the second slot in the cam to cause said hour hand to move back 1 hour, the lever thereafter being retracted.

OUTLINE OF THE DRAWINGS For a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawings, in which:

FIG. I is a rear view of a secondary clock having a setting mechanism in accordance with the invention, the seconds hand assembly of the mechanism being shown in its unactuated state;

FIG. 2 is the same as FIG. 1, but with the mechanism shown in its actuated state for setting the seconds hand;

FIG. 3 is a front view of the secondary clock, with the hour hand assembly of the setting mechanism shown in its unactuated state;

FIG. 4 is the same as FIG. 3, but with the mechanism shown in its actuated state for setting the hour hand; FIG. 5 is a section taken through the clock; and FIG. 6 is a block diagram of a master-secondary clock system in accordance with the invention.

DESCRIPTION OF THE INVENTION General Description of System Before analyzing the nature of the setting mechanism illustrated in FIGS. 1 to 5 and incorporated in each of the secondaries included in the master-secondary clock system, we shall first consider the system itself, as shown in FIG. 6.

p In a system in accordance with the invention, a master clock 10 placed at a central control station is linked by wire or radio means to a plurality of secondary clocks 11A, 11B, 11C, etc. at various points remote from the master clock.

Master clock 10 preferably is a battery-operated clock of the tuning fork type, such as that disclosed in my copending application, Ser. No. 160,835 filed July 8,197 l "Such clocks, which employ a high Q turning fork resonator as a time base, are far more accurate than other commercially available types of battery-operated timepieces, particularly those making use of balance wheels. However, since the master clock serves to regulate all secondaries in the system, in order to be most effective, it must possess an exceptionally high degree of accuracy.

For the purpose of stabilizing the tuning fork master clock, use is made of a crystal-controlled frequency standard 12 in an arrangement such as that disclosed in the Schaller US Pat. No. 3,282,042 wherein control pulses whose repetition rate corresponds to the assigned frequency of the fork, are derived by frequency division from a high-frequency crystal oscillator. These control pulses serve to synchronize the operating frequency of the fork and thereby to maintain the high accuracy of the master clock.

Alternatively, the battery-operated tuning-fork master mayrbe synchronized from the standard (US) A-C power line by multiplying the frequency of the 60 cycle voltage to say 240 cycles in order to govern the vibratory rate of a 240 cycle tuning-fork clock movement. Even in the event of an AC power failure and the resultant absence of a sync signal, the master tuning fork will still continue to keep good time, because of its inherent accuracy. However, the advantage of a crystalcontrolled system for the master clock is that it may be entirely battery-operated and therefore independent of power line failures. Another important advantage of a system which is entirely battery operated is that no wiring is necessary to link the clocks to the power line, thereby reducing installation expenses.

All secondary clocks in the system are also in the form of battery-operated tuning fork movements whose operation is independent of the power line. Because of the inherent accuracy and reliability of tuning fork clocks, the timing error in anyone of the secondaries is not likely, in any day, to be more than plus or minus a few seconds. Hence no need exists, as with conventional systems, to be concerned about minute hand correction.

Because the secondary clocks are quite accurate, it is only necessary, as a practical matter, to effect correction of the seconds hand. This need not be done every hour, but only once or twice every 12 hour period, say at 4 a.m., l a.m., 4 p.m. and p.m.

In a system according to the invention, a D-C pulse is fed from the master clock tothe secondary clocks just when the seconds hand of the master clock is about to reach the 60 position (the exact minute). This control pulse serves to actuate the seconds hand setting assembly of the setting mechanism in the secondary clock to cause the seconds hand thereof, in the event it deviates from the 60 position, to precisely assume that position, thereby bringing about registration between the master and the secondary clock.

In practice, D-C pulses for actuating the setting mechanism may be provided by a battery 13 coupled by a polarity-reversing switch 14 to a commutator switch 15, operated by the master clock. The commutator switch is arranged to produce a switch closure terminating at an exact minute, say at 4 oclock (a.m. and p.m.), thereby sending a DC pulse to the secondaries, the trailing edge of which is coincident with the exact minute.

The seconds hand setting action occurs regardless of the polarity of the D-C control pulse. When, however, the D-C pulse is transmitted to the secondaries between specified hours of a 12hour interval, say between 1 and 3 oclock, the control pulse will also then serve to actuate the hour hand setting assembly of the secondary clock, to shift this hand to the extent of a l-hour increment in a direction depending on pulse polarity, thereby effecting a transfer from Standard to Daylight Savings time or vice versa.

In actual operation, the proper polarity will be selected by switch 14 to set the hour hand forward in the Spring of the year. This polarity will thereafter be maintained for correcting the seconds hand of the clock until the Fall. At the time when the hour hand is set back one hour, the opposite polarity is used. This polarity will be in effect until the following Spring, at which time it will be again reversed. Thus, the purpose of the setting mechanism in each secondary clock is to permit the use of a D-C pulse, reversed at the proper time, to perform three functions; (a) setting the hour hand ahead, (b) setting the hour hand back and (c) setting the seconds hand.

The Setting Mechanism Referring now to the secondary clock shown in FIG. 5, it will be seen that this clock is provided with a seconds hand S attached to an arbor 16, coaxially disposed within a cannon 17 on which the minute hand M is mounted. Cannon 17 is concentrically supported for rotation within a tubular shaft 18 to which the hour hand H is attached.

These time indicating hands are driven by means of a clock motor 19, preferably of the battery-operated tuning-fork type. The output shaft 20 of the clock motor, which makes one revolution per minute, is coupled by a slip clutch 21 to the arbor 16 for the seconds hand. Arbor 16 has a pinion 22 keyed thereto that engages the first wheel in a dial train of gears of the type conventionally used to provide movement of the hour and minute hands at the proper rates relative to that of the seconds hand.

In a setting mechanism in accordance with the invention, a seconds hand setting assembly is provided at the rear of the dial train to effect correction of the seconds hand. This assembly includes a cam 23 mounted on the arbor l6 and rotating therewith, such that an angular shift in the cam position brings about a change in the position of the seconds hand. While this change is taking place, arbor 16 is effectively disconnected by the slip clutch from the clock motor.

The setting mechanism also includes an hour hand setting assembly at the front of the dial train. This assembly is provided with a cam 24 mounted on the tubular shaft 18 for the hour hand, such that an angular shift in this cam brings about a change in the hour hand position. The drive for the hour hand shaft includes a slip clutch so that the hour hand may be shifted by cam 18 without disturbing the remainder of the dial train.

In conjunction with FIGS. 1 and 2, we shall first consider the structure of the seconds hand setting assembly. Cam 23 of this assembly, which is mounted on arbor 16, is heart-shaped, and cooperates with a lever 25 pivoted on a post 33. Lever 25 is profiled to define a generally rectangular foot 25A which swings down into operative engagement with cam 23 when head 25B of the lever is pushed upwardly, either by pin 27 or by pin 28 projecting laterally from the front face of a toothed drive wheel 29.

The teeth of drive wheel 29 interrnesh with a pinion 30 mounted on the shaft of a D-C correcting motor 31, energized by D-C control pulses transmitted from the master clock of the system.

Motor 31 is preferably of the permanent magnet type but differs from conventional structures in that its armature coil has no iron core, and therefore this motor has a very low inertia. The reason for this type of motor is that when the motor is de-energized, its armature may easily be turned in the reverse direction by drive wheel 29 which is subject to torque by the springtensioned lever 25.

When a D-C pulse is applied to motor 31 in a given polarity, pinion 30 turns in one direction to cause rotation of wheel 29 in, say, the clockwise direction, in which event pin 27 on the wheel, as shown in FIG. 2, engages the end of a rectangular extension 25C on lever 25. Pin 27, moving in the clockwise direction, forces head 25B of the lever to move in the same direction, causing foot 25A to swing down toward cam 23.

When, however, the D-C pulse is applied to motor 31 in the reverse direction, the wheel 29 now turns in the counterclockwisedirection, in which event pin 28 on the wheel engages the left side of a triangular lever extension 25D, again raising head 25B and causing foot 25A to swing down in the direction of cam 23.

Thus, regardless of whether the polarity of the DC pulse is plus or minus, lever 25 will always be caused to shift in the same direction even though drive wheel 29 turns in a direction determined by the pulse polarity.

Lever 25 is normally maintained in the position shown in FIG. 1 and of engagement with cam 23 by means of a spring 32, one end of which is wrapped about a post 33 on lever 25, the other end pressing against a fixed pin 34.

When lever 25 is forced by a D-C pulse applied to motor 31 to swing toward cam 23, spring 32 is flexed and foot 25A of the lever which then engages cam 23, serves to push and thereby rotate this cam until the foot lies against the flat of the cam, as shown in FIG. 2, at which point the seconds hand setting assembly is stalled. In the stalled state shown in FIG. 2, the seconds hand on arbor 16 occupies the 60 position, to match the seconds hand on the master clock, which is on the exact minute.

For practical reasons, the arrangement is made such that the leading edge of the D-C pulse is slightly ahead of the exact minute at the master clock (i.e., about onehalf second in advance), whereas the trailing edge of the pulse is coincident with this exact minute. Hence, motor 31 is energized slightly before the exact minute, thereby allowing sufficient time for the lever action to take place to reset the secondshand.

At the trailing edge of the D-C control pulse, the motor is abruptly de-energized, at which point spring 32 then acts to retract lever 25. Head 258 of the lever then returns to its initial position (FIG. 1), in which state pins 28 and 29 are again both in engagement with extension 25C and 25D, respectively, in preparation for the next correcting pulse. In this retraction action,

' wheel 29 is turned, causing rotation of the de-energized low-inertia motor.

We shall now consider, in conjunction with FIGS. 3 and 4, the structure of the hour hand setting assembly. Cam 24, which is mounted on the tubular shaft 18 for the hour hand, is provided with a pair of angularly displaced triangular notches 24A and 248, which cooper- I ate with the spaced legs of a V-shaped lever 35, pivoted at its apex on a fixed post 36. When the lever swings toward the right, leg 35A engages notch 24A to turn cam 24 in the clockwise direction, and when the lever swings toward the left, leg 35B engages notch 248 to turn cam 24 in the counterclockwise direction.

Drive wheel 29 operated by the correcting motor pinion 30, is provided on its rear face with a pin 37, which engages a pair of parallel spring wires 38 and 39, extending from one side of foot 35B of the lever. When a D-C control pulse is applied to the motor, pin 37 on the wheel will move in the clockwise or counterclockwise direction, depending on pulse polarity.

When the pin 37 moves in the clockwise direction through spring wires 38 and 39, it causes lever 35 to swing toward the left, but when it moves in the counterclockwise direction, it causes the lever to swing toward the right (see FIG. 4).

In the unactuated state as shown in FIG. 3, the notches 24A and 24B on cam 24 are symmetrically disposed with respect to legs 25A and 35B of the lever. The arrangement is such that this symmetry exists only at exactly 2 oclock. Since cam 24 turns with the hour hand shaft, after 2 o'clock, the cam notches and lever legs proceed to move out of alignment.

If a D-C control pulse is sent at two oclock when the notches and legs are aligned, and the pulse polarity is such that leg 35B engages notch 24B, cam 24 will then turn in the counterclockwise direction from the 2 oclock to the 1 oclock position. With a reverse polarity pulse transmitted at 2 oclock, leg 35A will then engage notch 24A, causing cam 24 to turn in the clockwise direction from the 2 oclock to the 3 oclock position. Thus, depending on pulse polarity, the hour hand is moved back or ahead a l-hour increment.

As a consequence, the clock is corrected for Daylight Savings time, while at the same time, the seconds hand is returned to the 60 position should it be off time at the moment the Daylight Savings time correction signal is transmitted.

If the correction signal should be transmitted at any time other than between one and 3 oclock, the notches on cam 24 will not be aligned with the legs on lever 35, and the operative leg will then engage the circumference of the cam, in which event springs 38 and 39 will simply flex, permitting drive wheel 29 to complete its action to cause the seconds-hand setting assembly driven by the same wheel to set the seconds hand to the 60" position.

It is to be noted that in the clock, the seconds hand is geared directly to the minute hand, hence any repositioning of the seconds hand will automatically move the minute hand, thereby maintaining the proper phase relationship therebetween. I-Iowever, correction of the seconds hand-must, of necessity, be limited to errors no geater than about plus or minus 25 seconds, for otherwise, if the error of the seconds hand is greater than this amount,the correction of the seconds hand will result in an error in the setting of the minute hand. Since the tuning-fork secondary clocks are inherently quite accurate, the error of the seconds hand is not likely, in any day, to be more than plus or minus a few seconds; hence a correction of this error at least once a day or more often, will not permit the seconds hand error to go beyond the permissible range, and in effecting correction of the seconds hand, the minute hand will at the same time be properly set.

I Claim:

1. A master-secondary clock system provided with a master-clock disposed at a central control station and a plurality of secondary clocks at various remote points, each secondary clock having a seconds hand arbor and an hour hand shaft,

a. means at the master station to generate a D-C control pulse and to transmit said pulse to each of said secondary clocks in one polarity or in the reverse polarity; and

b. a pulse-responsive setting mechanism associated with each secondary clock, said mechanism being provided with a D-C motor actuating a drive wheel that is caused to turn in a direction determined by the polarity of the incoming pulse which is applied to said motor, said wheel when turning, operating both a seconds hand assembly and an hour hand assembly, said seconds hand assembly including a first lever which, when the wheel is turned in either direction, so engages a first cam mounted on said arbor, as to set the seconds hand to the 60 position, said hour hand assembly including a second lever which when the wheel is turned in one direction so engages a second cam mounted on said shaft as to advance the hour hand a 1-hour increment and when the wheel is turned in the reverse direction so engages the second cam as to move the hour hand back a 1-hour increment, said second cam being so profiled that the second lever is capable of effecting engagement therewith only when the control pulse is transmitted during a predetermined interval in the course of the day.

2. A system as set forth in claim 1, wherein said master clock is a battery-operated tuning-fork movement whose operating frequency is synchronized by pulses derived from a crystal-controlled frequency standard.

3. A system as set forth in claim 1, wherein said secondary clocks are all of the battery-operated tuningfork type.

4. A system as set forth in claim 3, wherein each of said secondary clocks include a slip clutch interposed between the seconds hand arbor and the tuning-fork timing motor.

5. A system as set forth in claim 1, wherein said D-C motor has a pinion on its shaft engaging the teeth of said drive wheel.

6. A system as set forth in claim 1, wherein said first cam is heart-shaped, and said first lever includes a foot which moves into engagement with said cam when a D-C pulse is transmitted.

7. A system as set forth in claim 6, wherein said first lever is provided with a rectangular extension engaged by one pin on said wheel and a triangular extension engaged by another pin thereon.

8. A system as set forth in claim 1, wherein said second lever is V-shaped to define legs which cooperate with a pair of spaced notches in said second cam, said legsand notches being symmetrically arranged only at one point in time. 

1. A master-secondary clock system provided with a master-clock disposed at a central control station and a plurality of secondary clocks at various remote points, each secondary clock having a seconds hand arbor and an hour hand shaft, a. means at the master station to generate a D-C control pulse and to transmit said pulse to each of said secondary clocks in one polarity or in the reverse polarity; and b. a pulse-responsive setting mechanism associated with each secondary clock, said mechanism being provided with a D-C motor actuating a drive wheel that is caused to turn in a direction determined by the polarity of the incoming pulse which is applied to said motor, said wheel when turning, operating both a seconds hand assembly and an hour hand assembly, said seconds hand assembly including a first lever which, when the wheel is turned in either direction, so engages a first cam mounted on said arbor, as to set the seconds hand to the ''''60'''' position, said hour hand assembly including a second lever which when the wheel is turned in one direction so engages a second cam mounted on said shaft as to advance the hour hand a 1-hour increment and when the wheel is turned in the reverse direction so engages the second cam as to move the hour hand back a 1hour increment, said second cam being so profiled that the second lever is capable of effecting engagement therewith only when the control pulse is transmitted during a predetermined interval in the course of the day.
 2. A system as set forth in claim 1, wherein said master clock is a battery-operated tuning-fork movement whose operating frequency is synchronized by pulses derived from a crystal-controlled frequency standard.
 3. A system as set forth in claim 1, wherein said secondary clocks are all of the battery-operated tuning-fork type.
 4. A system as set forth in claim 3, wherein each of said secondary clocks include a slip clutch interposed between the seconds hand arbor and the tuning-fork timing motor.
 5. A system as set forth in claim 1, wherein said D-C motor has a pinion on its shaft engaging the teeth of said drive wheel.
 6. A system as set forth in claim 1, wherein said first cam is heart-shaped, and said first lever includes a foot which moves into engagement with said cam when a D-C pulse is transmitted.
 7. A system as set forth in claim 6, wherein said first lever is provided with a rectangular extension engaged by one pin on said wheel and a triangular extension engaged by another pin thereon.
 8. A system as set forth in claim 1, wherein said second lever is V-shaped to define legs which cooperate with a pair of spaced notches in said second cam, said legs and notches being symmetrically arranged only at one point in time. 